What moral status does the human embryo have?
The moral status of the embryo is a controversial and complex issue. The main viewpoints are outlined below. [24]
1. The embryo has full moral status from fertilization onwards Either the embryo is viewed as a person whilst it is still an embryo, or it is seen as a potential person. The criteria for ‘personhood' are notoriously unclear; different people define what makes a person in different ways.
Arguments for this view
Arguments against this view
Development from a fertilized egg into to baby is a continuous process and any attempt to pinpoint when personhood begins is arbitrary. A human embryo is a human being in the embryonic stage, just as an infant is a human being in the infant stage. Although an embryo does not  currently  have the characteristics of a person, it  will become  a person and should be given the respect and dignity of a person.
An early embryo that has not yet implanted into the uterus does not have the psychological, emotional or physical properties that we associate with being a person. It therefore does not have any interests to be protected and we can use it for the benefit of patients (who ARE persons).
The embryo cannot develop into a child without being transferred to a woman's uterus. It needs external help to develop. Even then, the probability that embryos used for in vitrofertilization will develop into full-term successful births is low. Something that could  potentially become a person should not be treated as if it actually  were  a person
2. There is a cut-off point at 14 days after fertilization Some people argue that a human embryo deserves special protection from around day 14 after fertilization because:
After 14 days the embryo can no longer split to form twins. Before this point, the embryo could still be split to become two or more babies, or it might fail to develop at all.
Before day 14, the embryo has no central nervous system and therefore no senses. If we can take organs from patients who have been declared brain dead and use them for transplants, then we can also use hundred-cell embryos that have no nervous system.
Fertilization is itself a process, not a ‘moment'. An embryo in the earliest stages is not clearly defined as an individual.
3. The embryo has increasing status as it develops An embryo deserves some protection from the moment the sperm fertilizes the egg, and its moral status increases as it becomes more human-like.

Arguments for this view
Arguments against this view
There are several stages of development that could be given increasing moral status:
1. Implantation of the embryo into the uterus wall around six days after fertilization. 2. Appearance of the primitive streak - the beginnings of the nervous system - at around 14 days. 3. The phase when the baby could survive if born prematurely. 4. Birth.
If a life is lost, we tend to feel differently about it depending on the stage of the lost life. A fertilized egg before implantation in the uterus could be granted a lesser degree of respect than a human fetus or a born baby.
More than half of all fertilized eggs are lost due to natural causes. If the natural process involves such loss, then using some embryos in stem cell research should not worry us either.
We protect a person's life and interests not because they are valuable from the point of view of the universe, but  because they are important to the person concerned . Whatever moral status the human embryo has for us, the  life that it lives has a value to the embryo itself .
If we judge the moral status of the embryo from its age, then we are making arbitrary decisions about who is human. For example, even if we say formation of the nervous system marks the start of personhood, we still would not say a patient who has lost nerve cells in a stroke has become less human.
If we are not sure whether a fertilized egg should be considered a human being, then we should not destroy it. A hunter does not shoot if